The present invention relates to the operation of a hydroelectric plant, and more particularly to an adaptive method for controlling the operation of a hydroelectric plant.
The operation of the hydroelectric plant may be indirectly controlled by the frequency of an electrical grid that the generator is synchronized. The hydroelectric plant should respond to a load change, such as a step-change demand, in a appropriate manner allowing for maintaining the frequency within an allowable range.
Some hydroelectric plants use a control system that has an online control mode that uses a physical parameter as a control variable. The physical parameter may include, but is not limited to, generator output. The control system may incorporate different control philosophies; which may include: a Proportional-Integral-Derivative (PID) control algorithm; a programmed control curve that may be integrated with the PID; or the like.
The PID control algorithms typically use generator output as a process variable and a gate position as a control variable. Generally, this control philosophy requires high integral gains in order to respond effectively to a load setpoint change. PID control algorithms may be sufficient for large electrical grid applications. However, PID control algorithms may be insufficient for hydroelectric plants operating; in an isochronous mode, a small grid system, or an isolated power system. Moreover, if the hydroelectric plant is operated in those environments, the loading rate is relatively slow as the integral gains require compensating for those operating environments.
Generally, the programmed control curve philosophy incorporates pre-developed curve data that is used with a form of the PID control algorithm that incorporates feed-forward logic. The feed-forward logic may comprise a load ramping algorithm that incorporates the curve data to determine an opening position for a generator output setpoint and/or head value. The goal of the PID feed-forward logic may be to achieve a relatively fast and smooth response to load setpoint changes. The load ramping algorithm may incorporate the pre-programmed curve data to determine where the at least one opening should be positioned for a given load setpoint.
Although the PID feed-forward logic, described here may be beneficial. Older hydroelectric plants do not have pre-programmed curve data available. Furthermore, the high cost and time associated with upgrading the control system on these units prohibit the upgrade.
For the foregoing reasons, there is a need for a method and system of controlling a hydroelectric plant in a manner that provides for a relatively smooth and quick response to a load setpoint change, and allows for speed regulation during grid frequency disturbances, such as droop control. The method and system should not control require higher integral gains. The method and system should not require pre-programmed curves. The method and system should be adaptable to different operating environments, such as isochronous, small grids, large grids, isolated operation, or the like. The method and system should be adaptable to different hydroelectric turbine: designs, turbine mass, head value, or the like.